Dave is not a Samoan name so does not have a translation in the Samoan language. However, David is in the Bible, therefore has a translation as, of course, Samoa is a very religious nation. The Samoan translation of David is TAVITA.
Dan is not a Samoan name therefore has no actual translation in Samoan. If a Samoan boy was named Dan, his family would simply call him "Dan". HOWEVER, Daniel (which is in the Bible, therefore has a translation) in Samoan is Tanielu.
Jillian is not a Samoan name therefore does not have a Samoan translation. If a Samoan girl was named Jillian her family/friends would simply call her Jillian (or make up some sort of nickname for her).